I wonder why this never made it past the developmental stage. seems like good enough of an idea for production.

1950s. Start of the Jet era. No need for new prop planes for the military, and after WW2, the freight industry was glutted with vastly cheaper dc-6s and dc-7s.

Crazy, I was just thinking of something like this for modern Jets and the luggage section of the fuselage. Ie, the luggage handlers back the container at the luggage belt then the whole thing gets sent to the airplane. The closest I've seen in modern airplanes is bomb-resistance containers than hold maybe a dozen pieces of luggage.

Neat, but not nearly suicidal enough. The Me 323 on the other hand, now that's a one way trip.

Sure as hell would make house moving easy for mobile home owners.

If you look at the aerodynamics and structure of the concept---it looks like it it became the design study for the Fairchild C-119 "Flying Box Car" which had the similar boxy fuselage ---but wasn't detachable...

This actually seems like a good idea. But I suppose that air cargo has been "containerized" well enough now that most of the packing and unloading happens outside of the plane.

It's the same principal as the Virgin Galactic Spaceship 2 and White Knight. Rather than the cargo hold, it's the spaceship portion.